JPH05213216A - Motor-operated power steering device - Google Patents

Abstract

PURPOSE:To provide a steering sensation having high feeling by generating a proper assist force according to the driving state of a driver. CONSTITUTION:A motor-operated power steering device comprises a motor 6 coupled to a steering system and generating steering assist torque, a torque sensor 11 for detecting steering torque of a steering system, a car speed sensor 12 for detecting a car speed, and a control means 70 for controlling drive of the motor 6. Fuzzy inference is effected according to a given fuzzy rule based on a car speed and a steering angle by means of a steering angle sensor 41 for the steering angle of a steering system. A driving state estimating means 60 for estimating the driving state of a driver is provided and the control means 70 corrects a control value, by means of which driving of the motor 6 is controlled, based on a driving state estimated by the driving state estimating means 60.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electric power steering apparatus suitable for use in a vehicle, and more particularly to a power steering apparatus which assists a steering force with a rotational output of a motor.

[0002]

2. Description of the Related Art In recent years, electric power steering systems using a motor instead of a hydraulic type have been used as a vehicle power steering device, and the motor has an increasing tendency in the future due to advantages such as small size and light weight as an actuator.

FIG. 7 is a block diagram showing an example of a mechanical system of a conventional electric power steering apparatus. In this figure, the rotational force of a steering handle 1 is transmitted to a steering gear 2 including a pinion gear via a handle shaft. At the same time, it is transmitted to the rack shaft 3 by the pinion gear, and the wheels 4 are turned through the knuckle arms and the like. Further, the rotational force of the steering assist (auxiliary) motor (DC motor) 6 controlled and controlled by the control device 5 is transmitted to the rack shaft 3 by the meshing of the steering shaft 7 including the pinion gear and the rack shaft 3, and the steering wheel 1 is used. It will assist steering. The rotating shafts of the handle 1 and the motor 6 are mechanically connected by gears 2 and 7 and a rack shaft 3.

On the other hand, a steering torque sensor 11 (see FIG.
Steering torque (return torque) is detected by
The vehicle speed is detected by the vehicle speed sensor 12 (see FIG. 8). Then, the motor 6 is controlled by the control device 5 based on the detected torque, the vehicle speed, and the like. The control device 5 and the motor 6 have a battery 8 mounted on the vehicle.
Is supplied with its operating power.

The control device 5 includes detectors such as a current detector and a voltage detector, a drive circuit for driving the motor 6, a computer (CPU, for example, microprocessor) that controls the motor 6 as a whole, a memory, and a computer. It is composed of an interface circuit with the input / output device.

Next, FIG. 8 is a block diagram showing various functions of a computer incorporated in the control device 5 in a different manner.
It is drawn together with blocks showing output devices and various circuits. In this figure, the assist command unit 10 is supplied with the detected torque V _T of the torque sensor 11 and the detected vehicle speed V _{S of the} vehicle speed sensor 12. The assist torque value instruction function unit 13 in the assist command unit 10 outputs a command value representing the assist torque to be generated by the motor 6 according to the detected torque V _T.

Further, the multiplication constant function unit 14 detects the detected vehicle speed V _S
A constant is generated according to the above, and this constant is multiplied by the above-mentioned assist torque command value in the multiplication calculator 15. As a result, the assist torque value (or motor current command value) output from the multiplication calculator 15 becomes a value determined by the detected torque V _T and the detected vehicle speed V _S , as shown in FIG. 9.

FIG. 9 shows that when the steering torque V _T is in a certain range, a motor current almost proportional to the steering torque V _T flows (assist torque is generated) and exceeds the above range. as constant motor current flows (the assist torque is generated), also according to the vehicle speed V _S, the motor current (assist when when the vehicle speed V _S is high to reduce the motor current (assist torque), the vehicle speed V _S is low It indicates that an assist command for controlling the motor 6 is generated so that the torque is increased.

The detected torque V _T is also given to the phase compensator 16, and the phase compensator 16 adds the differential value of the detected torque V _T to the output of the multiplication calculator 15,
The output (reference current command value) of the assist command unit 10 is supplied to the current control unit 20.

On the other hand, in addition to the assist command unit 10, the output of the regenerative brake command output unit 30 is added to the current control unit 20. The regenerative braking instruction output unit 30 includes a steering angle sensor 31 that detects the steering angle of the steering wheel 1.
The command value for detecting the neutral position of the steering wheel 1 based on the output of the steering wheel 1 and for instructing the motor 6 to apply the regenerative brake near the neutral position of the steering wheel 1 based on the above-described detected torque V _T and the detected vehicle speed V _S. Is added to the output of the assist command unit 10 and is supplied to the current control unit 20 as a final current command value.

The current control unit 20 includes a PWM (Pulse) that follows the H-bridge drive method including, for example, four switching elements.
The motor 6 is driven and controlled by a chopper operation using a (Width Modulation) pulse, and current feedback control is performed. That is, the armature current detector 26 detects the armature current ia of the motor 6, and the target current command value and the detected current ia given by the current deviation calculator 21.
The deviation from and is calculated. The absolute value of the deviation is obtained by the absolute value converter 24, and the duty generator 25 determines the duty ratio of the PWM pulse based on the absolute value.

On the other hand, the polarity (positive or negative) of the above-mentioned deviation is discriminated by the positive / negative discriminating section 22, and the generated duty ratio and the discriminated polarity are given to the motor drive section 23, and the motor drive section 23 determines these values. Based on the above, the four switching elements wired in the H-bridge type are turned on / off to drive the motor 6.

[0013]

However, in the above-described conventional electric power steering apparatus, the driving state of the driver (driver), that is, the state in which the driver turns the steering wheel at the vehicle speed at that time (operating state). However, the steering assist torque based on the detected steering torque and the detected vehicle speed is uniquely determined,
For example, there is a problem that the driving feel is not good in sports driving, and the steering wheel feels heavy during relaxing driving, which deteriorates the feeling.

Therefore, an object of the present invention is to provide an electric power steering apparatus capable of generating an appropriate assisting force according to the driving condition of a driver and obtaining a steering feeling with a high feeling.

[0015]

In order to achieve the above object, an electric power steering apparatus according to a first aspect of the present invention is provided with an electric power steering apparatus, which is connected to a steering system and generates a steering assist torque, and a steering torque of the steering system. An electric power steering system including: steering torque detecting means for detecting the vehicle speed; vehicle speed detecting means for detecting the vehicle speed; and control means for controlling the drive of the motor based on the outputs of the steering torque detecting means and the vehicle speed detecting means. In the device, a steering angle detecting means for detecting a steering angle of a steering system, and a driving state estimating means for estimating a driving state of a driver by performing fuzzy inference according to a predetermined fuzzy rule based on the vehicle speed and the steering angle of the steering system. And the control means sets a control value for controlling the drive of the motor based on the driving state of the driver estimated by the driving state estimating means. Characterized in that it positive. Also,
As a preferred mode, the steering angle detecting means detects the applied voltage and the armature current of the motor, and calculates the steering angle of the steering system from the detection result.

[0016]

In the present invention, fuzzy inference is performed based on the vehicle speed and the steering angle according to a predetermined fuzzy rule to estimate the driving state of the driver, and the driving of the motor is corrected according to the estimated driving state. Therefore, an appropriate assist force is generated according to the driving state of the driver, and a feeling of steering with high feeling can be obtained. For example, the assisting force is weakened in sports driving and a suitable feeling is felt, and the assisting force is strengthened and a light steering feeling is obtained during relaxing driving.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the drawings. 1 to 6 are views showing an embodiment of an electric power steering apparatus according to the present invention. In explaining the present embodiment,
The same components as those of the conventional example are designated by the same reference numerals, and duplicate description will be omitted. FIG. 1 is a block diagram showing the hardware configuration of this apparatus.

In the figure, reference numeral 40 is a control device, and the control device 40 includes a steering torque sensor (steering torque detecting means) 11, a vehicle speed sensor (vehicle speed detecting means) 12, and a steering angle for detecting a steering angle of a steering wheel 1. An output signal from a sensor (steering angle detection means) 41 and a temperature sensor 42 that detects the temperature of the motor 6 is input, and the control device 40 includes an ignition switch 43.
And connected to the battery 8.

The control device 40 comprises a CPU 51 which controls the overall control of the motor 6, a relay drive circuit 52, a motor drive circuit 53, a motor current / voltage detection circuit 54 and a fail safe circuit 55. CPU
Reference numeral 51 calculates a processing value required for drive control of the motor 6 based on signals from the steering torque sensor 11, the vehicle speed sensor 12, the steering angle sensor 41, the motor temperature sensor 42, and the ignition switch 43, and outputs a PWM pulse to the motor drive circuit. Then, the motor drive circuit 53 drives the motor 6 in accordance with the PWM pulse.

The motor current / voltage detection circuit 54 detects the motor voltage and the motor current from the PWM drive pulse of the motor drive circuit 53 and outputs them to the CPU 51. In response to this, the CPU 51 calculates the rotation speed and the rotation acceleration of the motor 6 based on the detected motor current value and the motor voltage value, and according to a predetermined fuzzy rule using the vehicle speed, the steering torque, and the steering angle as input parameters. Fuzzy inference is performed to estimate the driving state of the driver, and the PWM drive pulse is controlled so as to correct the assist force according to the estimated driving state.

The fail-safe circuit 55 performs control such as stopping the operation of the motor drive circuit 53 based on the output of the motor current / voltage detection circuit 54 when the motor current or the like is abnormal. The relay drive circuit 52 operates the power relay 56 based on a command from the CPU 51 when the ignition switch 43 is in the ON state, and the motor drive circuit 5
The power of the battery 8 is supplied to 3.

The motor current / voltage detection circuit 54 has a function as a current detection means for detecting a motor current and a voltage detection means for detecting a motor voltage. The CPU 51 has a function as an operating state estimating means.

Next, FIG. 2 is a block diagram showing various functions of a computer incorporated in the control device 40, together with blocks showing other input / output devices and various circuits. This diagram differs from the conventional example in that the outputs of the fuzzy inference unit (corresponding to the driving state estimating means) 60 and the correction value calculation unit 61 are added to the output of the multiplication operation unit 15 in the assist command unit 10. .. The output signal of the vehicle speed sensor 12 and the output signal of the steering angle sensor 41 are input to the fuzzy inference unit 60. The output signal of the steering angle sensor 41 is the angle at which the steering wheel 1 is steered, and this corresponds to the steered amount, that is, the steering amount.

The fuzzy inference unit 60 uses the vehicle speed and the steering angle as fuzzy inputs to perform fuzzy inference according to a predetermined fuzzy rule, estimates the driving state of the driver, and outputs the estimated value to the correction value calculation unit 61 for correction. The value calculation unit 61 calculates a correction value for correcting the drive current of the motor 6 according to the estimated driving state of the driver, and the multiplication calculation unit 1
It is added to the output of 5 and output to the current control unit 20. The fuzzy inference unit 60 and the correction value calculation unit 61 constitute an assist correction unit 62. Further, the assist command unit 10 and the current control unit 20 form a control means 70.

Here, the fuzzy rule for estimating the driving state will be described. 3A and 3B are membership functions of the antecedent part, of which FIG. 3A is a membership function regarding the steering angle θ, and FIG. 3B is a membership function regarding the vehicle speed SP. Further, FIG. 3C is a fuzzy output in the consequent part, which is a membership function represented by a single tone position.

The meaning of the label in each membership function is as follows. NL: Negative Large (large in the negative direction) NM: Negative Medium (slightly large in the negative direction) NS: Negative Small (small in the negative direction) ZR: Zero (neutral) PS: Positive Small (small in the positive direction) PM : Positive Medium (slightly large in the positive direction) PL: Positive Large (large in the positive direction) However, the negative direction corresponds to the left-turned state of the steering wheel, and the positive direction corresponds to the right-turned state of the steering wheel.

The fuzzy rule is shown in FIG. 4, and is expressed by the following equation. The rule is so-called I
It is expressed in the form F, THEN (if any). R1. IF Vehicle speed = PS AND Steering angle = NL THEN Fuzzy output = NS (Relax) R2. IF vehicle speed = PL AND steering angle = NL THEN fuzzy output = NL (sports driving)

The fuzzy rule R1 means "if the vehicle speed is small in the positive direction and the steering angle is large in the negative direction, the fuzzy output is small in the negative direction and the driving state is relaxed running". ..

Further, the fuzzy rule R2 means "if the vehicle speed is large in the positive direction and the steering angle is large in the negative direction, the fuzzy output is large in the negative direction and the driving state is sports running". Is. Hereinafter, other rules are determined by the same method. The driving state means a state of sports running or relaxing running. Further, as a result of the fuzzy inference, if the absolute value of the output value is large, the degree of sports running is high, and if the absolute value is small, the degree of relaxing running is high.

Next, the operation of the power steering control will be described. FIG. 5 is a main program showing the processing of the power steering control. Ignition switch 4
When 3 is turned on, first, in step S1, the vehicle speed and the steering angle are read from the sensors 12 and 41, respectively, and then in step S2.
Then, the vehicle speed and the steering angle are used as fuzzy inputs to perform fuzzy inference according to a predetermined fuzzy rule to estimate the driving state of the driver.

After that, in step S3, the estimated value of the operating state is added to the output of the multiplication calculation section 15 as a fuzzy output and output to the current control section 20. As a result, the PWM drive pulse is controlled so as to correct the assisting force by the motor 6 according to the estimated operating state, and an appropriate assisting force corresponding to the operating state is generated.

The fuzzy inference in step S2 is shown in FIG.
It is executed by the subroutine shown in. In FIG. 3, first, the vehicle speed and steering angle are set to fuzzy inputs, and then step S
At 11, the processing of the condition part is performed. That is, the adaptability of the input is obtained from the input values (vehicle speed and steering angle) and the condition part membership function. Next, in step S12, the processing of the conclusion section is performed. That is, the fuzzy output for each label of the conclusion part is found by comparing the rule suitability found by the condition part processing with other suitability. Then, step S1
Weighting processing is performed in step 3 to adjust the degree of influence of each rule on the conclusion part. For example, the one having the smaller matching degree is selected and given to the consequent part. Then, in step S14, one definite value representing the fuzzy output is calculated.

That is, in the consequent part, the membership functions are superposed by the MAX combining process to generate a combined output, and then the defuzzifier obtains one definite value from the center of gravity of the combined output. In this way, the driving state is estimated, and as shown in FIG. 4, the modes of sports running and relaxing running are obtained.

As described above, in this embodiment, the driving state of the driver is estimated by performing the fuzzy inference according to the predetermined fuzzy rule based on the vehicle speed and the steering angle, and the driving force of the motor is corrected according to the estimated driving state. To be done. Therefore, the steering assist torque is not uniquely determined based on the detected steering torque and the detected vehicle speed, but an appropriate assist force is generated according to the driving state of the driver, and a high-feeling steering feeling is obtained. .. For example, the assisting force is weakened in sports driving and there is an appropriate feeling of response, and the assisting force is strengthened during relaxed driving and a light steering feeling can be obtained. Can be realized.

Although the steering angle is calculated from the output of the steering angle sensor in the above embodiment, the present invention is not limited to this. For example, the motor rotation speed is calculated from the voltage / current of the motor 6 and the integrated value is calculated. The steering angle may be calculated from the steering angle. With this configuration, the steering angle sensor is not needed, and the cost can be reduced.

That is, first, when the rotation speed dθ / dt of the motor 6 is obtained from the values of the motor voltage V _M and the motor current I _M , the rotation speed dθ / dt of the motor 6 represents the steering angular velocity, which is the steering angle. Will correspond to. afterwards,
The calculated value of the rotation speed dθ / dt of the motor 6 is integrated to obtain the steering angle. The rotation speed dθ / dt of the motor 6 is
The observer output is calculated from the motor voltage V _M and the value of the motor current I _M according to the following equation, which makes the steering angle sensor unnecessary. V _M = R _a I _M + K _e dθ / dt where R _{a is the} armature current, K _{e is the} induced voltage constant.

In this embodiment, the operating state estimating means for carrying out fuzzy inference is realized by software, but it may be realized by hardware using a fuzzy chip, for example.

[0038]

According to the present invention, since the driving state of the driver is estimated by fuzzy inference, it is possible to generate an appropriate assisting force according to the driving state of the driver, and the steering with high feeling can be obtained. You can get a feeling. For example, the assisting force is weakened in sports driving and a proper feeling of response can be obtained, and the assisting force is strengthened and a light steering feeling can be obtained during relaxing traveling.

[Brief description of drawings]

FIG. 1 is a block diagram showing a hardware configuration of an embodiment of an electric power steering apparatus according to the present invention.

FIG. 2 is a block diagram showing various functions of a computer incorporated in the control device shown in FIG.

FIG. 3 is a diagram showing a membership function used in fuzzy inference according to the embodiment.

FIG. 4 is a diagram showing a fuzzy rule of the embodiment.

FIG. 5 is a flowchart of a main program for power steering control according to the same embodiment.

FIG. 6 is a flowchart showing a fuzzy reasoning subroutine of the embodiment.

FIG. 7 is a configuration diagram showing an example of a mechanical system of a conventional power steering device.

FIG. 8 is a block diagram showing various functions of a computer incorporated in a control device of a conventional power steering device.

FIG. 9 is a diagram showing characteristics of assist torque of a conventional power steering device.

[Explanation of symbols]

6 Motor 10 Assist Command Unit 11 Steering Torque Sensor (Steering Torque Detecting Means) 12 Vehicle Speed Sensor (Vehicle Speed Detecting Means) 20 Current Control Unit 40 Control Device 43 Ignition Switch 51 CPU (Operating State Estimating Means) 52 Relay Drive Circuit 53 Motor Drive Circuit 54 motor current / voltage detection circuit (current detection means, voltage detection means) 55 fail-safe circuit 60 fuzzy inference section (operating state estimation means) 61 correction value calculation section 70 control means

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Claims (2)

[Claims] 1. A motor connected to a steering system for generating a steering assist torque, a steering torque detecting means for detecting a steering torque of the steering system, a vehicle speed detecting means for detecting a vehicle speed, the steering torque detecting means and the vehicle speed. In an electric power steering apparatus including: a control unit that controls driving of the motor based on an output of a detection unit, a steering angle detection unit that detects a steering angle of a steering system, the vehicle speed, and a steering angle of the steering system. Fuzzy inference according to a predetermined fuzzy rule based on, provided with a driving state estimating means for estimating the driving state of the driver, the control means, based on the driving state of the driver estimated by the driving state estimating means An electric power steering apparatus characterized by correcting a control value for controlling driving of the motor. 2. The steering angle detecting means detects an applied voltage and an armature current of the motor, and calculates a steering angle of the steering system from the detection result, and calculates the steering angle. Electric power steering device.